Sexually transmissible HPV infection is highly prevalent in the British population, particularly among young women, the second National Survey of Sexual Attitudes and Lifestyles (Natsal-2) has revealed. HPV DNA was detected in 29% of urine samples from women and 17% of samples from men.

Natsal-2 used a probability sample of the population aged 16-44 years, resident in Britain. A total of 11,161 people were interviewed face to face at home between May 1999 and February 2001.

A total of 5,026 respondents who reported at least one sexual partner were invited to provide a urine sample to test initially for genital chlamydia; 3,569 (71%) gave consent for the sample to be stored for anonymous future testing. Overall, 3,123 samples were adequate for testing using an in-house genotype assay for detection of a range of HPV types.

A total of 29.0% of samples from women and 17.4% from men showed an HPV DNA.

The WHO International Agency for Research on Cancer has identified 13 high-risk (HR) HPVs. Persistent HR-HPV infection (e.g. with types 16 and 18) has been associated with the development of cervical and other cancers. Low-risk (LR) HPV infection e.g. with types 6 and 11 is associated with the majority of anogenital warts.

HR-HPV infection was detected in 15.9% of women and 9.6% of men. The detected prevalence of either HR-HPV type covered by current vaccines (HPV types 16 and 18) was 5.5% in women and 3.0% in men, with 4.1% of women and 2.6% of men having only these types.

Overall, 9.8% of women and 4.8% of men had one of the types covered by the quadrivalent vaccine (6, 11, 16 and 18); 3.4% of women and 2.6% of men had two or more HR-HPV types detectable.

The prevalence of detectable HR-HPV declined with age in both men and women (from over one quarter of women aged 18-24 years to less than a tenth in women aged 40-44 years). HPV infection was also less frequent in those who were married but there was no association with educational status or social class.

Prevalence of HR-HPV fell with rising age of first sexual intercourse (more for men than women). It was also strongly associated with increasing numbers of lifetime partners and the total number of new partners in the previous year, partners without a condom and partner concurrency. Ever having had a same sex partnership was associated with HR-HPV in women but not in men. Smoking and alcohol consumption were significantly associated with HR-HPV in men and women, as was oral contraception use in women.

Factors most strongly associated with HR-HPV in women included: younger age, being unmarried, increasing number of new sexual partners in the past year and concurrency between the most recent sexual partners in the past year; and in men: younger age at first sex, increasing number of sexual partners without a condom in the past year and the number of new sexual partners in the past year.

Genital warts are the most commonly diagnosed viral sexually transmitted infection in the UK. Genital infection with HPV is often asymptomatic and undiagnosed.

An immunisation programme to protect young girls from acquiring HR-HPV (16 and 18) using a bivalent vaccine before becoming sexually active was introduced in the UK in 2008. A quadrivalent vaccine that also gives protection against LR-HPV (6 and 11) will be available from autumn 2012.

The study suggests sexually transmitted HPV is highly prevalent in the population. The findings of overall HPV DNA prevalence were similar to studies in the USA, as were the differences between men and women.

It also gives further evidence that some HR-HPVs are strongly associated with sexual behaviour, which supports the vaccination policy to protect young girls from cervical cancer before they become sexually active.

The prevalence figures for HPV 16 and 18 may also help to explain to women with abnormal smear tests how they might have acquired HPV and to help them understand that this is common and is likely to be sexually transmitted. This offers further ammunition for the safer sex message.

Dr Richard Ma